The present invention relates to sewer venting devices and, more particularly, to a sewer venting device which filters sewer gases vented to the atmosphere.
Sanitary sewer pipes or sewers carry raw sewage to treatment plants where the sewage is treated. Flow problems and other problems can develop as a result of accumulated pockets of gases within a sewer line. On the other hand, there are situations in which vacuums can occur which can also cause flow problems and structural problems. For these reasons, it is sometimes necessary to vent gases from sewers to the atmosphere to prevent pockets of gases from accumulating, and at other times it is necessary to draw air from the atmosphere into the sewer lines to prevent the development of vacuum conditions. At all times, it is necessary to prevent raw sewage from being released at such points of venting and/or admission of air.
Where possible, sewage systems are designed to allow sewage to flow by gravity to a treatment plant. However, in hilly areas, pressurized sewage techniques are needed in some locations to pump the sewage uphill on the way to a treatment plant. Typically, such systems make use of so-called “wet wells” which are collection reservoirs. When the level of sewage in the wet well rises to a selected level, a pump or pumps are activated to pump sewage out of the wet well and over a hill toward a treatment plant or to the next wet well. Initially, the sewer pipe is filled with air at ambient pressure. When the pump begins pushing the sewage along the sewer line, it is necessary to vent air from the pipe to enable the sewage to flow. When the sewage level in the wet well drops to an acceptable level, the pumps are deactivated. When the pumps are stopped, sewage within the line at the top of a hill tends to flow downhill in both directions from the hilltop. Unless air is allowed to be drawn into the sewer pipe at the hilltop, sewage flow is inhibited and vacuums can occur which can reach levels that will cause the sewer pipe to collapse.
Sewer venting valve arrangements have been developed to enable the outflow of gases from sewers and the inflow of air into sewers, while preventing the discharge of liquids and their suspended solids from the sewer. The model D-020 Combination Air Valve for Sewage, manufactured by A. R. I. Flow Control Accessories (www.arivalves.com or www.ari.co.il) is an example of such a valve. The model D-025 is a similar type of sewer venting valve. This sewer venting valve has a vertically elongated housing which connects to a sewer pipe at a lower end within a access chamber or manhole, a valve and seat at an upper end controlling flow to an outlet, and a valve control rod with a float on a lower end and connected to the valve at an upper end of the rod. The valve is normally in an open position such that gases can flow out from the sewer pipe or air can be drawn into the sewer, as necessary. However, the presence of a liquid within the housing raises the float, causing the valve to seat to prevent sewage from being discharged through the venting valve.
Such a sewer venting valve can be installed in communication with a sewer pipe at a hilltop location of a pressurized sewer system. The sewer venting valve allows air to be vented from the sewer pipe when the pipe is pressurized, prevents sewage liquids from being discharged when flow past the venting valve occurs, and allows air to be drawn back into the pipe when the pumps are deactivated to prevent vacuum conditions from forming within the pipe.
A problem with venting air and gases from a sewer pipe is the discharge of malodorous compounds within such gases which typically occur in sewage, including principally hydrogen sulfide and also methyl mercaptan, organic sulfides, amines, and other nitrogen and sulfur containing compounds.